Numerical simulation of liquid film around grid spacer with interface tracking method

Design studies of reduced-moderation water reactors (RMWR) are being carried out at JAERI as one candidate for the future reactors. The RMWR core adopts a hexagonal tight lattice arrangement with about 1 mm gap between adjacent fuel rods. To optimize the thermal design, the boiling transition (BT) in such a tight lattice core is one of most important subjects to be evaluated, but effects of the rod diameter, the rod gap and the spacer configuration have not been fully investigated. Thus, we made a plan to develop a mechanistic BT model to evaluate the geometry effects by a two-phase flow numerical simulation. In this paper, the results of TPFIT code with the advanced interface tracking method applied to the air-water two-phase flow simulations in rectangle duct are shown. (author)